A cutting tool insert for machining of a workpiece is attached to a cutting tool insert holder, which also may be referred to simply as a tool holder, and is used in a machine tool, such as a lathe, or milling machine. Cutting tool inserts having many different geometries are known. Namely, depending on what kind of cutting operation is to be performed on a workpiece, a relevant cutting tool insert must have a suitable geometry.
A cutting tool insert is commonly provided with two or more cutting edges. Thus, the cutting tool insert may be placed in two or more different positions in a relevant tool holder to expose one of the cutting edges at a time to engage with a relevant workpiece. Put differently, the cutting tool insert is indexable the same number of times as the number of cutting edges.
One example of a cutting tool insert geometry is that having two opposite rhombus side surfaces. Such a cutting tool insert is suited for cutting an inside right angle corner in a turning operation, i.e. remaining material of the workpiece extends at a 270 degree angle about the inside right angle corner. The cutting tool insert includes four cutting edges, i.e. the cutting tool insert is indexable four times. Each cutting edge includes a first cutting edge portion and a second cutting edge portion arranged at an acute angle. The first cutting edge portion may cut a workpiece along a first direction and the second cutting edge portion may cut the workpiece along a direction orthogonal to the first direction. A cutting tool insert coded CNMG is an example of one such cutting tool insert having two rhombus surfaces.
An eight times indexable cutting tool insert can also cut an inside right angle corner similarly as a cutting tool insert having two rhombus side surfaces. An example of an eight times indexable cutting tool insert is taught by US 2014/0064864.